1. Field of the Invention
The present invention relates to a surface treatment process on an OLED (organic light emitting display) panel and, more particularly, to a method for fabricating an OLED panel.
2. Description of Related Art
The OLED panels attract attentions of popularity because of their advantages such as light weight, high contrast of display, fast response rate, low power consumption and high brightness. Although many advantages can be found in the OLED display panels, lots of technical problems in manufacturing OLED display panels need to be overcome.
So far, the fabrication of OLED display panels is achieved by subsequently forming anode in parallel stripes, parallel photoresist ramparts, organic electroluminescent media and cathodes on the substrate of panels. The parallel photoresist ramparts acts as shadow masks as organic electroluminescent media and cathode materials are deposited on the exposed parallel anodes between photoresist ramparts. However, the lifetime of the OLED displays made by these processes is not long. The stability of the OLED displays and the yields of these manufacturing processes are poor. The short lifetime and the poor stability of the OLED display panels is resulted from direct contact between anodes and cathode materials in areas close to the border of pixels or the area close to the bottom of the sidewalls of photoresist ramparts. Since the border of the pixels are only roughly definded or separated by the photoresist ramparts and the anodes on the substrate, the contact between anodes and cathode materials cannot be effectively prevented. Therefore, the OLED display panels need an effective method to prevent the opportunity of electrical shorts between anodes and cathodes.
Recently, insulation layers made by SiO2 or photoresist are suggested to deposited or coated on the surface of the substrate to prevent possible electrical shorts. However, the process for fabricating SiO2 insulation layers on the substrate around the pixel areas is complicate and costs high. The process for fabricating SiO2 insulation layers on the OLED display panels is difficult to be applied to the mass-production of OLED display panels. On the other hand, since the insulation layer made by photoresist around pixels"" areas keep releasing organic solvent or water vapor from the photoresist slowly, the photoresist insulation layers become major sources of vapors to deteriorate the quality of the sensitive organic electroluminescent media on the OLED display panel. Therefore, the photoresist insulation layers also are the major factor that causes short lifetime and poor display quality. Moreover, the photoresists contain many photosensitive chemicals which decrease the photochemical stability of the photoresist insulation layers under high emission and shorten the lifetime of the OLED display panels. Therefore, the photoresist insulation layer is not a right answer to solve the problem illustrated above. Therefore, a method for fabricating a pixel-defining layer on the OLED panel to provide high yield of manufacturing, good stability of pixel-defining layers for preventing electrical shorts and extending the lifetime of pixels or OLED display panels are in demand.
Therefore, it is desirable to provide an improved method to mitigate the aforementioned problems.
The object of the present invention is to provide a method for fabricating a pixel-defining layer on an OLED panel to clearly define the area of the pixels on said OLED panel and to separate cathodes from anodes for avoiding shorts.
Another object of the present invention is to provide a method for fabricating a pixel-defining layer on an OLED panel to increase the stability of the pixel-defining layer for electricity, heat and light, and extend the lifetime of said OLED panel
Another object of the present invention is to provide a method for fabricating a pixel-defining layer to produce non-photosensitive polyimide pixel-defining layer stably and increase the yield.
To achieve the object, the method for forming a pixel-defining layer on an OLED panel of the present invention includes:
(A) providing a substrate;
(B) forming a plurality of first electrodes in parallel stripes on said substrate;
(C) coating a layer of non-photosensitive polyimide or polyimide precursor compositions on said substrate with said first electrodes;
(D) first prebaking said substrate with said layer of said non-photosensitive polyimide or polyimide precursor compositions;
(E) coating a layer of photoresist compositions on said layer of said non-photosensitive polyimide or polyimide precursor compositions;
(F) second prebaking said substrate with said layer of said photoresist compositions;
(G) forming patterns of said photoresist by exposing said substrate to masked radiaion and developing said photoresist on said substrate;
(H) etching said layer of said non-photosensitive polyimide or polyimide precursor compositions to form a patterned layer of said non-photosensitive polyimide or polyimide precursor compositions;
(I) releasing or stripping said patterned layer of said photoresist compositions; and
(J) baking said substrate with patterned non-photosensitive polyimide or polyimide precursor compositions for crosslinking or curing said patterned non-photosensitive polyimide or polyimide precursor compositions to form said pixel-defining layer.
The method for forming a pixel-defining layer on an OLED panel of the present invention can further includes: (K) forming a plurality of photoresist ramparts on said substrate and selectively on said first electrodes or said stripes of said polyimide pixel-defining layer; wherein said photoresist ramparts protrude from said substrate and the top sections of said ramparts are about parallel to the surface of said substrate.
The method for forming a pixel-defining layer on an OLED panel of the present invention can further includes: (L) depositing organic electroluminescent media to the exposed area between said ramparts on said substrate or said first electrodes; and (M) forming a plurality of second electrodes on said organic electroluminescent media on said substrate or said first electrodes.
The method for forming a pixel-defining layer on an OLED panel of the present invention can selectively further comprising forming a plurality of auxiliary electrodes on or beneath the surface of said substrate before forming a plurality of said first electrodes on said substrate.
The method for forming a pixel-defining layer on an OLED panel of the present invention can selectively further comprising forming parallel photoresist ramparts having T-shape cross-section on said non-photosensitive polyimide pixel-defining layer, and said patterns of said photoresist are parallel stripes.
The OLED panel of the present invention comprises: a substrate; a plurality of first electrodes in parallel stripes, said first electrodes locating on the surface of said substrate; a plurality of non-photosenstive polyimide pixel-defining layers, said non-photosenstive polyimide pixel-defining layers selectively locating on said substrate or on said first electrodes; a plurality of photoresist ramparts, said photoresist ramparts selectively locating on said first electrodes or on said pixel-defining layer; a plurality of organic electroluminescent media, said organic electroluminescent media locating in the exposed area between said ramparts on said substrate; and a plurality of second electrodes, said second electrodes locating on said organic electroluminescent media; wherein each said ramparts protruding from said substrate and having an overhanging portion projection in a direction parallel to said substrate; and said photoresist ramparts are formed through coating a compositions of photoresist on said substrate, exposing said substrate to masked radiation and development.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.